[Gllug] OT: Mains electricity colour coding.

[Chris Bell]

On Mon 25 Oct, Gerd Busker wrote:

> In many countries brown/blue are completely interchangeable.  I think 
> the UK is one of the few countries where a plug is phase/neutral 
> specific, even though many countries indeed tie blue to ground somewhere 
> along the line, certainly if it is actually 1 tap of a 3-phase system 
> (which almost all power is).
> 
> If you look at a 220V shaver socket, there both pins are "floating" 
> (with the help of a transformer).  If you grab one (don't do this at 
> home) in theory you bring it to neutral and the other end is live so 
> you're safe!
> 
> My house in holland had both blue and brown live at ~110V in opposing 
> phase - I was never sure if this was by design or not.
> Bascically you treat blue as live, since it often can be.
> 
> Gerd.
> 
> 

   The UK regulations require PME (Protective Multiple Earths) with the
neutral connected to earth at the meter termination. This allows the
electricity supply to use a single earth/neutral cable which should not
carry significant current when there is approximate balance between the
three phase currents. All metal installed in a building should be earthed,
including all metal window frames and plumbing, even when isolated from any
other metal by e.g. plastic pipes, and in theory even including the metal
handle in a glass door.
   Southern Electric deliberately unbalanced the supply here for over a year
when the feeder developed a short between phases, so they moved one of the
connections to the wrong phase. They eventually had to fix the fault and
replace the transformer before it burst into flames.

-- 
Chris Bell www.chrisbell.org.uk (was www.overview.demon.co.uk)
Microsoft sells you Windows ... Linux gives you the whole house.

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